Species and size compositions and reproductive biology of rays (Chondrichthyes, Batoidea) caught in target and non‐target fisheries in eastern Indonesia

Abstract

Extensive surveys of various fish landing sites in eastern Indonesia, conducted between April 2001 and March 2006, recorded a total of 54 species of batoid rays belonging to 12 families. The Dasyatidae was by far the most speciose family, comprising half of the recorded species, and was also the most abundant, contributing 89 and 44% to the total numbers and total estimated biomass of batoids, respectively. The size and sex compositions of 23 species of rays are described and an accurate size at maturity of males, i.e. with 95% CI, was determined for 13 of these species. The sex ratios were found to be close to parity in the majority of species, however, the landings of the whitespotted guitarfish Rhynchobatus australiae consisted of significantly more females than males, a situation also recorded for this species in the by‐catch of the northern Australian prawn fishery. Data on aspects of the reproductive biology of three dasyatid species (Dasyatis cf. kuhlii, Dasyatis zugei and Himantura walga), which form a substantial component of the by‐catch of the bottom trawl fisheries in the region, were collected on most sampling occasions. These small rays, i.e. maximum sizes 243–379 mm disc width, were found to have no distinct seasonal reproductive cycle and small litter sizes, i.e. less than four embryos. Opportunistic reproductive data, e.g. litter size and embryo sizes, were also collected from various other species. The litter sizes of the rhynchobatid and rhinobatid species examined were found to be larger than those of the gymnurid and dasyatid species examined, i.e. seven to 19 and two to 13 v. one to four, respectively. The data presented in this paper for the numerous species of rays which are landed by target and non‐target fisheries in Indonesia represent the first such data for the vast majority of these species.